This application claims benefit of Korean patent application number P2000-0866, filed Feb. 23, 2000, which is hereby incorporated by reference for all purposes as if fully set forth herein.
1. Field of the Invention
This invention relates to a tape carrier package for mounting an integrated circuit and a liquid crystal display containing the same, and more particularly to a tape carrier package with a window through which an alignment between the tape carrier package and a printed wiring board can be confirmed with the naked eye.
2. Description of the Related Art
Generally, an active matrix liquid crystal display uses thin film transistors (TFTs) as switching devices to display a natural-looking moving picture. Since such a liquid crystal display device can be made into a smaller-size device than a cathode ray tube, it is commercially viable for use as a monitor such as a portable television or a lap-top personal computer or other consumer device.
The active matrix liquid crystal display displays a picture corresponding to video signals such as television signals on a pixel (or picture element) matrix having pixels arranged at each intersection between gate lines and data lines. Each pixel includes a liquid crystal cell for controlling a transmitted light quantity in accordance with a voltage level of a data signal from a data line. A TFT (thin film transistor) is installed at an intersection between a gate line and a data line to switch a data signal to be transferred to the liquid crystal cell in response to a scanning signal (i.e., a gate pulse) from the gate line.
Such a liquid crystal display requires a number of integrated circuits (ICs) connected to the data lines and the gate lines to apply data signals and scanning signals to the data lines and the gate lines, respectively. The ICs are installed between the printed wiring board (PWB) and the liquid crystal panel to apply signals supplied from the PWB to the data lines and the gate lines. IC mounting methods include chip on board, hereinafter referred to as “COB”, tape automated bonding, hereinafter referred to as “TAB”, and chip on glass, hereinafter referred to as “COG”. (Other methods are also possible). The COB system is mainly used for a monochromatic liquid crystal display having a pixel pitch of more than 300 μm. As shown in FIG. 1, in this COB system, ICs 8 are mounted on a PWB 6 and a heat-seal connector 10 connects the PWB 6 and a glass substrate 3 in a liquid crystal panel 2. In this case, a back light unit 4 used as a light source is provided between the liquid crystal panel 2 and the PWB 6. As shown in FIG. 2, in the TAB system, ICs 14 are mounted on a tape carrier package (TCP) 12. The TCP 12 is connected between the PWB 6 and the liquid crystal panel 3. As shown in FIG. 3, in the COG system, an IC chip 20 is directly mounted on a glass substrate 17 in a liquid crystal panel 16.
The above-mentioned TAB IC mounting method has been widely employed because it can widen an effective area of the panel and has a relatively simple mounting process.
As shown in FIG. 4, the TCP 12 employed in the TAB system includes a base film 22 on which is mounted an IC 14. The base film 22 is also provided with input and output pads 24 and 26 connected to input and output pins of the IC 14. The input and output pads 24 and 26 are fixed with the base film 22 by an adhesive layer 16 coated on the rear surface of the base film 22. The input and output pads 24 and 26 have a two-layer structure in which copper(Cu) is plated with tin(Sn) for preventing oxidation. As shown in FIG. 5A, the input pads 24 of the base film 22 are connected, via an anisotropic conductive film (ACF) 28, to pads 32 on a PWB 34. Likewise, the output pads 26 of the base film 22 are connected, via the ACF 30, to data/gate pads on the liquid crystal panel 2.
FIG. 5A and FIG. 5B illustrate a process of adhering the TCP to the PWB with the ACF 28. The input pads 24 are adhered to the bare film 22 by a bonding layer 16 coated on the base film 22. Conductive particles are coated on the ACF 28. The TCP 12 and the PWB 34 are adhered to each other by applying a certain pressure at a desired temperature after the ACF 28 has been coated. As shown in FIG. 5B, the conductive particles 30 coated on the ACF 28 are connected between the input pads 24 and a wiring 32 of the PWB 34 after the adhesion of the TCP 12 to the PWB 34 to form a current path.
Because the base film 22 has a low light transmissivity which adhered to the PWB, it is impossible to confirm an alignment state between the input pads and the wiring of the PWB. Accordingly, significantly bad alignments may be produced in the process of adhering the TCP to the PWB. Also, since the liquid crystal panel made from a glass transmits light even after the adhesion of the TCP to the PWB, alignment can be confirmed using a microscope; whereas, since the PWB does not transmit light, alignment cannot be confirmed using a microscope. Thus, a strong light is irradiated onto the base film to determine an alignment extent by a light reflected from the input pads. However, this method is complicated and unable to accurately determine an alignment. Also, such a method is time consuming.